Mobile platforms such as aircraft commonly include multi-layer structures such as sandwich-type composite structures to form various structural portions of their frames. Such structures can comprise an alveolar or cellular structure forming an internal layer lined on each side with a skin. The cellular structure may have a honeycomb configuration and the skins may be made from an impermeable material.
In aeronautics and especially in the maintenance of aircraft, it can be important to detect the presence of water in such structures. The presence of water may be an indication that one of the skins has been damaged and can also affect the worthiness and the weight of the structures. Typically, the presence of water in sandwich-type composite structures is detected either by regular inspections during maintenance procedures or by visible signs of its presence. However, portions of such structures may not be visible and can require some disassembly in order to be inspected. Some current non-destructive inspection (NDI) methods for detection of water ingress in such structures are limited to cases where water has accumulated on the inspection side of the structure as in the case using conventional ultrasonic probes and/or can require significant disassembly of part(s) of the mobile platform to permit radiography inspection. Such disassembly may be relatively labor intensive and may increase the cost and the time requirements for inspection.
Improvement is therefore desirable.